The Disconnect Between Short- and Long-Term Population Projections for Plant Reintroductions

The reintroduction of rare species in natural preserves is a commonly used restoration strategy to prevent species extinction. An essential first step in planning successful reintroductions is identifying which life stages (e.g., seeds or large adults) should be used to establish these new populations. Following this initial establishment phase, it is necessary to determine the level of survival, growth, and recruitment needed to maintain population persistence over time and identify management actions that will achieve these goals. In this 5-year study, we projected the short- and long-term population growth rates of a critically endangered long-lived shrub, Delissea waianaeensis. Using this model system, we show that reintroductions established with mature individuals have the lowest probability of quasi-population extinction (10 individuals) and the highest increase in population abundance. However, our results also demonstrate that short-term increases in population abundances are overly optimistic of long-term outcomes. Using long-term stochastic model simulations, we identified the level of natural seedling regeneration needed to maintain a positive population growth rate over time. These findings are relevant for planning future reintroduction efforts for long-lived species and illustrate the need to forecast short- and long-term population responses when evaluating restoration success.

Assisted migration as a climate change adaptation strategy: lessons from restoration and plant reintroductions

Climate change is thought to threaten between 25% and 50% of global plant biodiversity. In response to this looming crisis, the calls for the translocation, or assisted migration, of species to ensure the survival of this biodiversity have been increasing. The concept has its detractors, and is not without risk, but few studies have documented the success of the approach or veracity of the risk. Here we review both the ecological restoration literature and the plant reintroduction literature to discover insights into the promises and pitfalls of translocating species as an adaptation strategy in the face of our changing climate. Although habitat restoration and the assisted migration of rare plant species have different objectives and goals, they share the practice of translocating species from their site of origin to a new one. It is primarily the scale at which the movement of those species occurs that distinguishes the two.